A great many azo dyes have been proposed over the past century which contain sulfonic acid substituents. Such dyes have traditionally found application as acid dyes for wool fabric materials. Although extensive research has been conducted in this area of dye chemistry over the past century, recent demands for dyes with specific properties applicable to new fabric materials have rendered most of such early dyes inapplicable to modern needs. As one example of a specialized area of dye application may be mentioned carpet dyeing. In the dyeing of carpets, it is necessary to provide a dye with excellent "transfer". The transfer properties of a dye relate to the ability of the dye to produce level dyeings even in heavy fabrics and with filaments of a large diameter. Nylon carpeting represents a prime example of such a fiber material which requires a dye having excellent transfer properties. Other problems which occur in the dyeing of nylon carpeting are occasioned by variations in the carpeting itself; for example, nylon carpeting may have localized areas of differing crystallinity, due perhaps to differing stresses established in the drawing to which the fiber is subjected during manufacture. Such localized areas accept the acid dyes at different rates and in varying amounts, depending upon the physical characteristics of the carpet in each area. With a dye of excellent transfer properties, it is possible to dye the carpeting with an evenness not possible with dyes lacking such transfer properties. In addition to transfer properties, fastness to light is also an important consideration.
We have discovered a new series of acid dyes which dye polyamide fiber material, in particular carpet material, in bright reddish yellow hues. The dyeings are characterized by outstanding lightfastness and transfer and reserve properties.
Water insoluble dyes bearing some structural resemblance to the dyes of the invention are known. Carmichael in U.S. Pat. No. 3,497,495 discloses monoazo dyes containing methylsulfonyl groups and N-acetoxyethyl groups. However, these dyes, being water insoluble, are recommended for polyester and, if used to dye nylon, would dye all forms of nylon to essentially equal depths. In contrast, the dyes of the invention have a very marked difference of affinity for different types of nylon, such as the Types 844, 845, 846, and 847 BCF nylons.
Felix and Capeller in U.S. Pat. No. 2,354,187 disclose N-(carboxy substituted benzoxyethyl)monoazo dues and N-(carboxysubstituted alkyloxyethyl)monoazo dyes that contain the methylsulfonyl group. These dyes are water soluble because of the presence of the carboxyl group and they are structurally dissimilar because the solubilizing group is on the ester portion of the molecule. These dyes said to be particularly useful for dyeing cellulose ethers.
Felix and Huber in U.S. Pat. No. 2,045,324 disclose the possibility of making N-acetoxyethylazo dyes which could be water soluble, depending on the choice of diazotizable aryl amine base. The dyes disclosed in this patent are disclosed as colors for wool, silk and cellulose.